than that
which T. B. had seen before.

"This is our spare bedroom," said Dr. Fall, easily; "we seldom use it."

T. B. slipped into the apartment and made a quick scrutiny. There was
nothing of a suspicious character here.

"I hope you are satisfied now," said Dr. Fall as he led the way out,
"and that your two friends below are not growing impatient."

"You have seen them, then," said T. B.

"I have seen them," said the other gravely. "I saw them a few moments
after you entered the hall. You see, Mr. Smith," he went on, "we do not
employ anything so vulgar as bells to alarm us. When the entrance door
opens, a red light shows above my bed. Unfortunately, the moment you
came in I happened to be in an adjoining room at work. I had to go into
my bedroom to get a paper, when I saw the light. So, though I am perhaps
inaccurate in saying that I have been keeping you under observation from
the moment you arrived, there was little you did which was not
witnessed. I will show you, if you will be good enough to accompany me
to my room."

"I shall be delighted," said T. B.

He was curious to learn anything that the house or its custodian could
teach him. Dr. Fall's room was on the first floor, immediately over the
entrance hall, a plain office with a door leading to a cosily, though
comparatively expensively furnished bedroom. By the side of the doctor's
bed was a round pillar, which looked for all the world like one of those
conventional and useless articles of furniture which the suburban
housewife employs to balance a palm upon.

"Look down into that," said the doctor.

T. B. obeyed. It was quite hollow, and a little way down was what
appeared to be a square sheet of silver paper. It was unlike any other
silver paper because it appeared to be alive. He could see figures
standing against it, two figures that he had no difficulty in
recognizing as Ela and Johnson.

"It is a preparation of my own," said the doctor. "I thought of taking
out a patent for it. An adjustment of mirrors throws the image upon a
luminous screen which is so sensitive to light that it can record an
impression of your two friends even in the semi-darkness of the hall."

"Thank you," said T. B.

There was nothing to do but to accept his defeat as graciously as
possible. For baffled he was, caught at every turn, and puzzled,
moreover, by his extraordinary experience.

"You will find some difficulty in opening the door," said the pleasant
Doctor